The Salomon XA Advanced Skin S-Lab 12 is an ultra form-fitting pack for longer, serious trail running comes in two sizes for precise fit. Includes organizing pockets in the main compartment, and Sensifit construction, a stretch breathable mesh that literally wraps the pack and it’s contents around the body for a secure, non-binding, abrasion-free fit. Large enough to carry hydration and required equipment for UTMB and other long endurance races. PVC / BPA free bladder.